Process for the treatment or removal of impurities in a hydrometallurgical extraction process

Abstract

A Process for the treatment or removal of impurities, such as arsenic, antimony or bismuth, generated as by-products during smelting and refining of copper concentrates, comprises subjecting the by-products to pressure oxidation along with a copper concentrate in a hydrometallurgical copper extraction process or the treatment of impurities when present in a concentrate by subjecting the concentrate to a hydrometallurgical extraction process.

I claim:  
     
       1. A method of treating a by-product from a copper smelting or refining process, which by-product contains an element selected from the group consisting of As, Sb, Bi and Hg, comprising the steps of: 
       subjecting a copper ore or concentrate also containing iron and a source of bisulphate or sulphate ions to pressure oxidation at an elevated temperature and pressure in the presence of oxygen and an acidic solution containing halide ions; and  
       subjecting said by-product to the pressure oxidation together with said ore or concentrate to obtain a resulting pressure oxidation slurry containing copper and a compound of said element.  
     
     
       2. The method according to  claim 1 , wherein the compound of said element is a ferric compound. 
     
     
       3. The method according to  claim 1 , wherein the by-product is in solid form and is injected along with said copper concentrate into an autoclave in which said pressure oxidation is effected. 
     
     
       4. The method according to  claim 1 , wherein said pressure oxidation slurry is subjected to a liquid/solid separation step to obtain a pressure oxidation filtrate and a solid containing the compound of said element. 
     
     
       5. The method according to  claim 4 , wherein said pressure oxidation filtrate is recycled to the pressure oxidation and wherein said by-product is in liquid form, the by-product being combined with the pressure oxidation filtrate being recycled to the pressure oxidation. 
     
     
       6. The method according to  claim 5 , wherein the pressure oxidation filtrate contains copper in solution and further comprising the step of recovering copper from the filtrate prior to the recycle thereof. 
     
     
       7. The method according to  claim 5 , further comprising the step of subjecting the pressure oxidation filtrate and the by-product to evaporation prior to the recycle thereof. 
     
     
       8. The method according to  claim 5 , further comprising the step of subjecting the pressure oxidation filtrate and the by-product to neutralization prior to the recycle thereof. 
     
     
       9. The method according to  claim 4 , wherein the solid from the pressure oxidation contains copper and further comprising the step of subjecting the solid to an acidic leaching to obtain a copper solution and a solid residue containing the compound of the element. 
     
     
       10. The method according to  claim 9 , further comprising the step of recovering copper from the copper solution. 
     
     
       11. The method according to  claim 1 , wherein the iron and said element is present in a ratio of at least 1:1. 
     
     
       12. The method according to  claim 11 , wherein said ratio is about 3:1. 
     
     
       13. The method according to  claim 1 , wherein the pressure oxidation is carried out at a pH value of at least 2. 
     
     
       14. The method according to  claim 13 , wherein the pressure oxidation is carried out at a pH value of above 2.5. 
     
     
       15. The method according to  claim 1 , wherein the pressure oxidation is carried out at a temperature of from about 125° C. to about 160° C. 
     
     
       16. The method according to  claim 15 , wherein pressure oxidation is carried out at a temperature of about 150° C. 
     
     
       17. A method of treating a copper ore or concentrate also containing fluoride comprising the steps of: 
       subjecting the ore or concentrate along with a source of bisulphate or sulphate ions to pressure oxidation at an elevated temperature and pressure in the presence of oxygen and an acidic solution containing halide ions, the halide ions being selected from the group consisting of chloride ions and bromide ions, to obtain a resulting pressure oxidation slurry;  
       subjecting the slurry to a liquid/solid separation step to obtain a resulting pressure oxidation filtrate and a solid residue; and  
       continuously recycling the pressure oxidation filtrate to the pressure oxidation, thereby to solubilize the fluoride up to a saturation concentration in the pressure oxidation filtrate, to establish an equilibrium condition whereby no further nett dissolution of fluoride takes place and substantially all fluoride in the ore or concentrate goes into the solid residue.  
     
     
       18. The method according to  claim 17 , further comprising the steps of: 
       subjecting the solid residue to an acidic leaching to obtain a leach solution and a solid leach residue; and  
       continuously recycling the leach solution to the acidic leaching thereby to solubilize the fluoride up to a saturation concentration in the leach solution to establish an equilibrium condition whereby no further nett dissolution of fluoride into the leach solution takes place.  
     
     
       19. The method according to  claim 17 , further comprising the step of recovering copper from the pressure oxidation filtrate prior to the recycle thereof. 
     
     
       20. The method according to  claim 18 , further comprising the step of recovering copper from the leach solution prior to the recycle thereof. 
     
     
       21. A method of dispensing with an impurity contained in a first copper ore or concentrate, which impurity is in the form of an element selected from the group consisting of As, Sb, Bi and Hg, comprising the steps of: 
       subjecting a second copper ore or concentrate also containing iron and a source of bisulphate or sulphate ions to pressure oxidation at an elevated temperature and pressure in the presence of oxygen and an acidic solution containing halide ions; and  
       subjecting said first copper ore or concentrate by-product to the pressure oxidation together with said second ore or concentrate to obtain a resulting pressure oxidation slurry containing copper and a compound of said element.